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DIPHENYL, PERCHLORATES, PYRYLIUM compounds, AMMONIUM acetate, and NAPHTHYRIDINES

4-Ethyl-3-formyl-2,6-diphenylpyrylium perchlorate was obtained from 2,6-diphenylpyrylium perchlorate in three steps. Its reaction with triethyl orthoformate was accompanied by rearrangement of the initial pyrylium ring and led to pyrano[3,4- c]pyran-7-ium perchlorate system through a domino process involving ethanol addition-elimination. A plausible mechanism of the reaction is suggested on the basis of DFT quantum-chemical calculations. Reaction of the obtained pyrano[3,4- c]pyran-7-ium perchlorate with ammonium acetate led to a 2,7-naphthyridine derivative without a skeletal rearrangement. [ABSTRACT FROM AUTHOR]

ADDITION polymerization, EPOXY compounds, PYRYLIUM compounds, BULK solids, and IODONIUM salts

Cationic polymerization is a powerful tool when it comes to adhesive, coating, composite, and bulk material production. A variety of monomers is suitable for this technique, however epoxy‐based systems are used in many applications, due to their high reactivity and versatility. With the introduction of the radical induced cationic frontal polymerization (RICFP), an even more efficient pathway to cure epoxides and with it a variety of new applications was obtained. The prevailing initiator class for RICFP applications is the iodonium salt. Decades of research and fine‐tuning of the formulations lead to a highly effective and versatile initiator system. With the introduction of bismuth‐ and oxygen‐based onium salts for frontal polymerization, the well‐known iodonium salt is challenged. Bismuthonium hexafluoroantimonates shows high rate of polymerization and conversions of 84% in an epoxy system. The advantage of bismuthonium‐based systems is the pot life of the formulations, which can be cured at the press of a button. In this study, iodonium salts last around 3 days before a significant viscosity increase is measured, while the bismuthonium initiator lasts over 10 times as long with no significant drop in reactivity or frontal velocity. [ABSTRACT FROM AUTHOR]

SMALL molecules, LIPIDS, ANTIBIOTICS, BENZENE, and PYRYLIUM compounds

Recently we described a novel di-benzene-pyrylium-indolene (BAS00127538) inhibitor of Lipid II. BAS00127538 (1-Methyl-2,4-diphenyl-6-((1E,3E)-3-(1,3,3-trimethylindolin-2-ylidene)prop-1-en-1-yl)pyryl-1-ium) tetrafluoroborate is the first small molecule Lipid II inhibitor and is structurally distinct from natural agents that bind Lipid II, such as vancomycin. Here, we describe the synthesis and biological evaluation of 50 new analogs of BAS00127538 designed to explore the structure-activity relationships of the scaffold. The results of this study indicate an activity map of the scaffold, identifying regions that are critical to cytotoxicity, Lipid II binding and range of anti-bacterial action. One compound, 6jc48-1, showed significantly enhanced drug-like properties compared to BAS00127538. 6jc48-1 has reduced cytotoxicity, while retaining specific Lipid II binding and activity against Enterococcus spp. in vitro and in vivo. Further, this compound showed a markedly improved pharmacokinetic profile with a half-life of over 13 hours upon intravenous and oral administration and was stable in plasma. These results suggest that scaffolds like that of 6jc48-1 can be developed into small molecule antibiotic drugs that target Lipid II. [ABSTRACT FROM AUTHOR]

FURANS synthesis, ISOXAZOLES, PYRYLIUM compounds, PERCHLORATES, RING formation (Chemistry), and SODIUM nitrites

Ring contraction of 2,4,6-triarylpyrylium perchlorates by use of sodium nitrite mediated by ionic liquid has been used as a new, direct, and environmentally benign method for synthesis of bioactive 2-aroylfuran and novel 3,5-diaroyl-4-arylisoxazole derivatives in excellent yields. The versatility of the approach enables rapid and simple access to these pharmaceutically important compounds. The products were readily isolated from the reaction mixture by simple filtration. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

POLYMETHINES, DIHYDROPYRAZOLES, QUINOLIZINES, PYRYLIUM compounds, FLUORINATION, PERCHLORATES, ALDEHYDES, and NUCLEAR magnetic resonance spectroscopy

Unsymmetrical polymethine dyes have been synthesized from 6- tert-butyl-4-methylthioflavylium perchlorates and nitrogen-containing heterocyclic aldehydes derived from julolidine and polyfluorinated triphenyl-4,5-dihydro-1 H-pyrazoles. Spectral characteristics of the obtained compounds have been studied. [ABSTRACT FROM AUTHOR]

CHEMICAL synthesis, PYRYLIUM compounds, PHENYL ethers, FRIEDEL-Crafts reaction, and ACYLATION

Bis-acyl derivatives of diphenyl sulfide and diphenyl ether were synthesized by successive Friedel-Crafts acylations with 2-bromo-2-methylpropanoyl bromide and acetyl chloride. The subsequent reaction with sodium p-toluenesulfinate afforded the corresponding sulfones, and condensation of the latter with benzaldehyde in acetic acid in the presence of perchloric acid gave pyrylium salts with a β-ketosulfonyl fragment in the side chain. [ABSTRACT FROM AUTHOR]

PYRYLIUM compounds, CATIONS, PYRIDINIUM compounds, CHARGE exchange, and PHOTOINDUCED electron transfer

A physical organic analysis of a collection of 57 data sets generated by B3LYP/6-311+G(2d,p) geometry optimizations and TD-DFT calculations is presented. The analysis engenders recommendations for syntheses of new pyrylogen electron-transfer sensitizers that are potentially optimized for low energy absorbance and high extinction coefficients. It is argued that bathochromically shifted intense absorbance is especially useful to avoid competitive absorbance by electron-transfer substrates and for use at the low concentrations likely achievable in experimentally attractive nonpolar solvents. [ABSTRACT FROM AUTHOR]

CHEMICAL synthesis, PYRYLIUM compounds, CYANIDES, CHEMOSELECTIVITY, ANIONS, CHEMORECEPTORS, OPTICAL spectroscopy, and FLUORESCENCE spectroscopy

The high-yield one-pot synthesis of a novel chemosensor based on a 4-methyl 2,6-diphenyl pyrylium trifluoromethanesulfonate (Pyr) salt that absorbs in the visible region is reported. The ability of pyr to sense various anions has been investigated using UV–visible spectroscopy and fluorescence spectroscopy. Pyr selectively detects CN− in competition with various other anions such as Cl− , Br− , I− , SCN− , ClO4− , NO3− , HSO4− and PF6− , due to its highly reactive nature towards nucleophiles. The selective detection of CN− with pyr gave rise to a significant hypochromic effect in CH3CN solution at λmax387 and 446 nm, which are the absorption and fluorescence peaks, respectively. These studies indicated a high affinity of CN− for pyr, and forming a 1:1 ratio leads to cyano-enone derivative. [ABSTRACT FROM AUTHOR]

PHOSPHINE synthesis, PYRIDINE, CHEMICAL synthesis, HETEROCYCLIC compounds synthesis, and PYRYLIUM compounds

The microreview covers three, most powerful, strategies of the synthesis of phosphinine (systematically called phosphabenzene) starting from pyrylium salts, five-membered heterocycles, and reagents with C≡P bond. [ABSTRACT FROM AUTHOR]

PYRYLIUM compounds, STOKES shift, OPTICAL properties, LASER beams, and MOLECULAR magnetic moments

The photophysical properties of molecular layers on dielectric support are studied for two pyrylium compounds, characterized by the presence or absence of a long styrene fragment in a molecule. It is shown that in the absence of a styrene fragment the layer absorption spectrum is significantly broadened in comparison with the spectrum of the solution of the starting compound and the Stokes shift is increased fivefold owing to a long-wavelength shift in the fluorescence maximum. Exposure of the layers to a high-power laser radiation also leads to a long-wavelength shift of the fluorescence spectrum and shows that the molecular layers exhibit high photoresistance compared to solutions of the same compounds. The orientation angles of the absorption transition dipole moments in the molecules of pyrylium compounds are estimated and change in the orientation angles in the course of successive irradiations by a series of nanosecond laser pulses is determined. [ABSTRACT FROM AUTHOR]

HETEROGENEOUS catalysts, PERCHLORATES, ORGANIC solvents, CHEMICAL reactions, PYRYLIUM compounds, and ALUMINUM oxide

The work described herein employs neutral alumina as an effective catalyst for ring opening of triarylpyrylium perchlorates to corresponding aromatic cyanodienones, which have main roles in biological activities. The present porous catalyst has several advantages, it is inexpensive, thermally and mechanically stable, nontoxic, and highly resistant against organic solvents. It increases the reaction rate many fold when compared with conventional reaction conditions. Moreover, the recovered alumina can be used several times without serious decrease in activity. [Supplementary materials are available for this article. Go to the publisher's online edition ofSynthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] [ABSTRACT FROM AUTHOR]

PYRYLIUM compounds, OXIDATION-reduction reaction, OXYGENATION (Chemistry), OCTANE, ANTIMALARIALS, PEROXIDES, and BIPHENYL compounds

Benzo-fused 1,4-diaryl-2,3-dioxabicyclo[2.2.2]octanes 4a- d ( 4a: Ar = CH, 4b: Ar = p-FCH, 4c: Ar = p-MeCH, 4d: Ar = p-MeOCH) were synthesized by 2,4,6-triphenylpyrylium tetrafluoroborate (TPPBF)-sensitized photoinduced electron-transfer (PET)-promoted oxygenation reactions, and their in-vitro antimalarial activity was evaluated. The results showed that these substances have sufficiently high activity to enable them to serve as antimalarial lead compounds. In addition, TPPBF-biphenyl-cosensitized PET oxygenation was shown to be an efficient method for introduction of an O-O moiety in the construction of antimalarial cyclic peroxides. Graphical Abstract: New antimalarial bicyclic peroxides 4 were synthesized by TPPBF-sensitized photoinduced electron-transfer oxygenation reactions.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

CHEMICAL synthesis, CHEMICAL reactions, PYRYLIUM compounds, PHENYL group, SUBSTITUTION reactions, and SALTS

α-monosubstituted pyridiniums were readily prepared by the one-pot reaction of their corresponding pyrylium salts and primary amines. This result shows that such kind of pyridiniums can be prepared via this route. It was proved that the number of phenyl groups at the pyrylium ring had a crucial effect on this one-pot synthetic route. [ABSTRACT FROM AUTHOR]

PYRYLIUM compounds, ENANTIOSELECTIVE catalysis, CATALYSTS, IONIC liquids, and ANIONS

A general and highly enantioselective synthesis of oxygen heterocycles from readily available in situ generated pyrylium derivatives has been realized by embracing a multi‐coordination approach with helical anion‐binding tetrakistriazole catalysts. The high activity of the tetrakistriazole (TetraTri) catalysts, with distinct confined anion‐binding pockets, allows for remarkably low catalyst loadings (down to 0.05 mol %), while providing a simple access to chiral chromanones and dihydropyrones in high enantioselectivities (up to 98:2 e.r.). Moreover, experimental and theoretical studies provide new insights into the hydrogen‐donor ability and key binding interactions of the TetraTri catalysts and its host:guest complexes, suggesting the formation of a 1:3 species. CApTive lock‐key model: Oxygen heterocycles were synthesized in high enantioselectivities from pyrylium derivatives by embracing a multi‐coordination approach with helical anion‐binding tetrakistriazole catalysts. New insights into the hydrogen‐donor ability and key binding interactions suggest the formation of a high‐order host:guest complex. [ABSTRACT FROM AUTHOR]

ENZYME analysis, OXYGEN isotopes, PYRYLIUM compounds, ISOBARIC processes, PROTEOMICS, and CHEMICAL labeling

Abstract Enzymatic 18O exchange, the well-established approach in comparative proteomics, has some disadvantages such as back exchange of labeled oxygen and overlapping the peak of a labeled peptide with isotopic peaks of an unlabeled one. Herein we demonstrated a simple procedure in which samples digested with a trypsin (with and without H 2 18O) were reacted with unlabeled and quadrupled 13C-labeled pyrylium salt respectively which results in formation of pyridinium cations. Thus, each isobarically labeled peptide containing zero or four 13C atoms in the mass reporter group, during tandem MS/MS forms an unique reporter ion useful for a relative quantitation. Such a sample treatment improves the signal to noise ratio, reduces overlapping of the isotopic peaks and completely eliminates the back exchange problem. Graphical abstract Image 1 Highlights • Formation of the isobaric peptides derivatives (duplex) in two samples compared. • A combination of enzymatic incorporation of 18O and reaction with 13C pyrylium salt. • The MS/MS experiment generates diagnostic ions shifted by 4 Da. • It solves the problem of overlapping of the isotopic peaks in the 18O approach. • Method eliminates the risk of back-exchange and increase of the ionization efficiency. [ABSTRACT FROM AUTHOR]

PYRYLIUM compounds, CHEMICAL reactions, RING formation (Chemistry), CRYSTAL structure, and STEREOSELECTIVE reactions

A convergent approach allowed total synthesis of (±)‐Englerin A, and its truncated analogues, employing a thermal 1,3‐dipolar cycloaddition of a highly substituted pyrylium ylide with vinyl acetate as the key step. The key intermediate, a 8‐oxabicyclo[3,2,1]octane oxygenated at the C6 position, was directly converted into a truncated Englerin A analogue. CuI catalyzed conjugate addition of vinyl Grignard to an enone, ozonolysis, and epimerisation of the resulting aldehyde allowed stereoselective introduction of the side‐chain leading to a total synthesis of the racemic natural product. The developed chemistry will allow synthesis of more complex analogues of the natural product based on the use of the key bicyclo[3,2,1]octane scaffold. Total synthesis of (±)‐Englerin A and a number of truncated analogues was developed based on a 1,3‐dipolar cycloaddition of a substituted pyrylium ylide. The bicyclic enone scaffold was further converted into a truncated analogue and the natural product. Interesting stereochemical effects of the bridgehead substituents on the reactivity of the 8‐oxabicyclo[3.2.1]octanes were uncovered. [ABSTRACT FROM AUTHOR]

ORGANIC chemistry, ORGANIC synthesis research, PYRYLIUM compounds, and CHEMICAL reagents

PYRYLIUM compounds, DYE-sensitized solar cells, and TIME-dependent density functional theory

Abstract Here, we discuss the formation of several heterocyclic benzopyrylium compounds via joint experimental-theoretical efforts, in order to obtaining a better understanding of the diverse properties of these interesting organic species. Our results suggest these benzopyrylium dyes as interesting sensitizers in the novel design of new solar cells from the basis of their optical properties and pH-dependent characteristics. The role of aromatic stability of the pyrylium compounds in the obtained properties is discussed in terms of both NBO and analysis of the induced magnetic field toward the isotropic respond. Furthermore, optical properties were analyzed in the framework of TD-DFT methodologies. Noteworthy changes in red-shift and absorptions λ max are observed that contribute toward the interesting DSSCs applications. Additionally, the emission profile of 2a derivative was obtained in agreement to both theoretically and experimental strategy. We expect that our results can be informative for further development of heterocyclic benzopyrylium compounds and their application in DSSCs devices. Graphical abstract Image 1 Highlights • Formation of benzopyrylium compounds via joint experimental-theoretical efforts. • Benzopyrylium dyes as interesting sensitizers in the novel design of new solar cells. • Optical properties were analyzed in the framework of TD-DFT methodologies. • Aromatic stability in terms of NBO and induced magnetic field to isotropic respond. [ABSTRACT FROM AUTHOR]